Dot n Dab - what's causing a damp spot?

[starboya]

We've had a builder baton and plasterboard our cellar. it was fairly dry down there and had been rendered fairly roughly decades ago.
For the majority of the room he used batons screwed to the walls, painted with damp proof membrane, plasterboard and skimmed.
There was one place on the wall at the bottom of the stairs that was damp though. There he removed the loose render and painted on a damp proof membrane. Then fitted plasterboard with dot n dab.
We're now 3 months on and a couple of circles of damp about the size of a 10p coin have appeared corresponding to where the adhesive for the plasterboard is. Does anyone know what's the likely cause and what should we do to fix it. I will call him back to look at it but I'd like to know what's going on and how it should be properly remedied first. Thanks

 

[1john]

He probably damaged the membrane while applying dabs, it's gonna have to come off I'm afraid.

 

[dann09]

There are P/B adhesives that claim to be moisture resistant. Perhaps, open it up and try again.

How would applying a few dabs of adhesive damage the "membrane"?

But, how could any professional expect a coating ( membrane/tanking ) to resist ground water pressure? I'm not referring to householders, why should you know technical stuff.

Here's a thing, i've never seen a commercial basement tanking installation that was not the full monte, including pumps and dimpled sheeting etc. - or even, in a large retail mall, with concrete barrier walls and pumps.

 

[1john]

If you have a painted on membrane, which could well be bitumen, i think it would be quite easy to break through it with the corner of a trowel when dabbing.